The present invention relates in general to monitoring traffic surrounding a motor vehicle, and, more specifically, to a method and apparatus for classifying on-board and in real time a traffic density within which a host vehicle is moving.
For a variety of automotive systems and functions, it can be useful to have available an estimate of local traffic density (including estimations of traffic density in the direct forward path of the vehicle, in adjacent lanes, and an aggregate or overall traffic density in the vicinity of the vehicle). For example, the warning thresholds (e.g., distances or buffer zones) for a collision warning system may be adjusted depending on whether traffic density is light, medium, or heavy. In addition, a driver alertness monitoring system may use different thresholds according to the traffic density.
Conventionally, traffic density estimations have been obtained in various ways. In one automated technique, a rough estimate of traffic density is found by tracking cell phones passing through designated roadway locations (e.g., a central monitor obtains GPS or cell tower-based coordinates of individual phones, maps them onto roadway segments, calculates a vehicle density, and communicates the result to the vehicles). Other automated techniques for counting the number of vehicles present at a road segment can also be used. These approaches give only a general idea of how many vehicles are within a fixed area (i.e., not specific to the immediate area around any particular vehicle). They have other disadvantages including that the update rate is slow, the vehicle must have wireless communication in order to access the information, and infrastructure must be provided for performing the calculations outside of the host vehicle.
In another approach, drivers or other observers may visually characterize the amount of traffic in an area. This is subject to the same disadvantages, and may be less accurate. In yet another approach, a Vehicle-to-Infrastructure system may be used to characterize the traffic density. This is subject to high costs of implementing hardware on both the vehicles and the roadside. Additionally, a sufficient market penetration would be needed in order for this to be feasible.